Pitot deicer



Nov. 4, 1958 J. H. ILIICKEY 2,853,698

PITOT DEICER Filed Nov. 20. 1953 ZIIIIIIIIIIII 12 I/ N VIIIIIIIIII fg w' 4 /4 4 2 22 I 28 r I --34 J v %/i a Him 31c ATTORNEYS United States Patent 6 PITOT DEICER John H. Hickey, Port Washington, N. Y. Application November 20, 1953, Serial No. 393,525

4 Claims. (Cl. 73-212) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. i

This invention relates to a device for preventing ice from forming around Pitot tubes.

The Pitot static tube is used in aeronautics to give the air speed of the airplane by combining a Pitot tube and a static tube or piezometer to form a pressure nozzle, and when used with a manometer, will determine the relative speed of a fluid. At low altitudes the Pitot tube operates efliciently to indicate the speed of the airplane. However, when high altitudes are used, the temperature drop is great and ice will form around the Pitot tube mouth, causing inaccurate determinations of air speed. Many attempts have been made to reduce the formation of ice, but with limited success. For example, it has been proposed to heat the Pitot tube, electrically, or in other ways, but the excess drain on the battery makes it inadvisable to use the deicing means continuously.

The instant invention overcomes the prior failures in the application of the principles of the vortex or Hilsch tube. In this manner, the inlet of the Pitot tube is maintained in ice free condition at all times and at a minimum of cost and maintenance.

A primary object of the invention is to provide a device that will prevent ice formation on the air speed indicating means of an airplane.

Another object of the invention is to provide a device that employs the principle of the vortex tube to use the heat obtained by the whirling motion of the air in the chamber to prevent ice formation on an air speed indicator.

More specifically it is an object of the invention to introduce a vortex tube in proximity to the Pitot tube used in aircraft to provide the heat necessary to prevent formation of ice when the aircraft attains high altitudes.

Another object of the invention is to provide a heat producing means that requires no moving parts and therefore, no maintenance.

Still another object of the invention is to provide a device that is simple and economical in construction, is readily installed and is strong and desirable for its intended use.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a vertical section of the invention,

'Fig. 2 is an end view of the device,

Fig. 3 is a section taken on line 33 of Fig. 1,

Fig. 4 is an enlarged detail of the heat producing means of the invention, and

Fig. 5 illustrates a vortex tube per se and the tangential air entry nozzle.

The vortex tube employed in the invention is illustrated in Fig. 5 and is of the counterflow type where the two an axial outlet tube E and is the cold orifice.

streams of gas travel in opposite directions. The vortex tube consists of a cylindrical tube A with a conduit nozzle B entering the cross-section tangentially at C at the outer periphery of tube A. While any point of entry on the periphery may be used, it is generally desirable to do so closer to one end of the tube. The end furthest away is the hot end and contains a restrictive member D acting as a throttle valve, while the end nearest the nozzle has In operation, the working fluid, generally air, enters conduit B and is discharged into cylinder A tangentially, creating a vortex. A portion of the fluid, depending on design and control, discharges through the hot side and the remainder through the cold outlet. Several theories have been advanced to explain the principle of operation. The most accepted one concerning the vortex tube-efiect considers the temperature differences obtained as due to a migration of kinetic energy due to viscous shear stresses within the rotating mass of gas produced by the vortex formed when fluid under ram pressure (or under pressure), enters the chamber. This vortex adheres to the law of constant angular momentum, where the velocity times the radius of any particle is a constant. Thus the inner radius of the tube near the axial center is small, and the radius increases towards the inner periphery of the tube with the tangential velocity highest at the axis of the tube and least at the periphery. This is an example of irrotational flow. Velocity distribution is changed by the'tendency of any viscous flow to equalize its velocity distribution as the vortex expands axially and the irrotational flow changes to rotational flow. This changing velocity distribution causes transfer of kinetic energy outward from the tube axis. The kinetic energy transfer raises the temperature of the outer gas layer and lowers the temperature of the inner layers. However, since a temperature difference exists in the gas, a heat transfer results, where the heat energy flows from the hot outer layers to the cold inner layers. A rotational flow near the axis builds up and the pressure of the gas increases, as well as a pressure gradient towards the cold orifice. While this rotational flow builds up, the innermost layers separate and proceed out of the cold orifice, this action continuing until the irrotational flow is changed to a rotational one. The remaining gas, under rotational flow, travels axially and out of the hot end of tube A. The difference in temperature of the two streams is due to the overall kinetic energy flow outward being greater than the heat flow inward.

Referring to the invention in detail, the application of the vortex tube as a means to prevent formation of ice around a Pitot tube is illustrated in Figures 1-4. Housing 10 includes the usual Pitot tube 12 and annular static tube 14. These tubes are connected by conduits 16 and 18 respectively to a manometer (not shown), by means of which the relative air speed is determined. Such expedient is well known and need not be further explained.

Surrounding Pitot tube 12 is an annular chamber 20 adapted to receive heated air from vortex tube 22. Spent hot air is exhausted by means of conduit 24 through the rear of housing 10.

Vortex tube 22 comprises a cylindrical pressure chamber 26 having tangential inlet 28 admitting built up ram, or air pressure by means of inlet conduit 30. At one end of chamber 26 is an axial outlet 32 for removal of the cold air to the atmosphere through passage 34. A' coaxial annular outlet 36 is provided at the other end of vortex chamber 22 for removal of the hot air. Bafile 38 is held in spaced relation from the inner walls of chamber 22 by any suitable means, such as spiders 40, at the outlet end 36 to provide the annular outlet means for removal of the hot air stream.

In operation, the modified Pitot tube is placed under Patented Nov. 4, 1958 the, wings of an aircraft, orrin any desiredflpositionrtos obtain air speeds. Ordinarily, at high altitudes, there would be a danger of ice formation around the mouth of; the." tube; rendering it useless;

periphery o-ftthe chamber. is; approached;

chance; passage .2 of; cold: airi through: the opposite side of- .chambers. 26; producedzih the vortexch'amber toip assintoannnlar cham ber. 20v. Chamber 2D: closelysurrounds Pitot tube 1 2 1 and; serves. to :maintaina the 1 temperature: sufficiently high 1 to. prevent icezformati'oruvaroundLthe: mouth ofth'e 'tuber Heated air is constantly: supplied to chamber- 20': bymeans of the continuous action-of vortex' tube 22 while: thewaircraft isein motion. Spent'air. is-exhausted to theatmosphere! by means: of conduit 24;

The deviceiisvery: effective, 7 for thereare n'o moving parts to be maintained; Performanceis therefore reliable and the cost 'ofinstallation is at a minimum.

Obviously manyi modifications and variations of the" present invention are 'possible in the light of the; above teachings. It is therefore to be understood that within the..scope:of the appended claims the invention may be practiced otherwise than'as specifically deseribed.

What is-claimed isz Annularioutlet 36: enables the hot an 1. v A .Pitot structure comprisingan elongated'body; said a body being provided with a-Pitot passageway having an inlet portion, a first chamber surrounding and substantially coextensive with the length of the inlet portion of said Pitot passageway, a circular vortex chamber mounted in said body and communicating. at one end thereof with said first named chamber, a discharge outlet in said vortex chamber and means prov'idi-hgian air i'nlet passage in said body and tangentially connected to saiduvortex chamber opposite the errd communicatihgwith saidfirstch'amber, whereby cold and'heated'layers ofif-airare obtained and the heated layer enters said first chamber and the cold layer is dischargedthrough' said discharge outlet.

2. The combination-of claim: 1; wherein, said-t vortex chamber includes a bafile adjacent the end communicating with said first chamber and means securing said bafiie in spaced relation from the walls of the vortex chamber to discharge the heated layer" in -an' annular stream.

3'. The-combination ofclaim 2; whereinsaid first cham' berlincludes'an' exhaust conduit extending throughsaid body to exhaust spentheated' airto"the"atmosphere.

4. The combination of" claim 3 wherein said vortex chamber is positioned normal to the longitudinal axis'of the first cham'berand said cold airdischarge' outlet is axially connected to said vortex chamber;

References Gited in the file of this patent UNITED STATES "PATENTS 

